The matrix proteins of bones and teeth play key roles in the structure and function of these tissues. Our objective is to study the structure and function of these macromolecules and to understand the regulation of their expression. The structures of bone and tooth matrix proteins have been studied by constructing recombinant cDNA libraries from bone or ameloblast cell mRNA. cDNAs encoding several bone and tooth matrix proteins were isolated. The clones and antibodies were used to determine the primary structure and mode of expression of the genes in cultured cells and intact tissue. The corresponding genomic DNAs have also been isolated and used to determine the intron-exon organization of these genes and the elements that potentially regulate their expression during development. Studies are underway using transgenic mice to identify the function of the matrix proteins and the elements that regulate their expression during development and aging in vivo.